President Obama’s turn on Jon Stewart’s Wednesday comedy show was a bit of bait and switch, in that the tone, the content, and the message turned out to be pretty darn serious. It was a half-hour that would have fit nicely in rotation with those Sunday morning shows – think “Meet the Press” or “Face the Nation.”

Yes, the comedian tweaked the president a few times, notably in Mr. Obama's choice of Lawrence Summers – Bill Clinton’s former Treasury secretary – to help steer the course out of the financial meltdown. Noting that the commander in chief had run as a candidate on the platform of hope and change, Mr. Stewart pointed out, “that’s pretty much exactly the same person” – a line that got a hearty audience laugh.

But laughter was in short supply on this presidential pre-election campaign stop. Stewart threw out some questions that weren't exactly softballs, suggesting that Obama's first two years in office have felt “timid” to supporters who expected transformation in Washington. But then he settled in for a good listen while the president hotly (for him) refuted that charge and ticked off his accomplishments: a health-care package that achieved “90 percent” of what he’d hoped, including a provision for young people to remain on their parents' insurance policies until age 26; reform of the credit-card industry; and an economy that is now adding jobs rather than shedding them.

There was a light moment when Stewart pointed out a campaign ad in which a candidate pulls out a rifle and takes aim at the cap and trade carbon-emissions bill, intoning that this was to be expected from a Republican. But wait, he said, “that was a Democrat!” More applause and audience hoots.

There was no stopwatch on the commentary, but it’s safe to say that in this 23 or so minutes of what is usually fast-paced comedy, even with serious guests, the president talked most of the time without a laugh line in sight. He did manage to lift his sights slightly to the “laughter, please” plea flashing in some offstage producer’s eyes as the show signed off. Obama brought up Stewart’s Saturday rally on the Washington Mall all by himself. Maybe if the rally had happened two years ago, things might have been different, the president said.

Not exactly a thigh-slapper, but the audience whooped it up as a great idea. Then he offered his own plug, “Just go vote.” Enthusiastic applause and more audience ruckus ended what was a rather sober half-hour of late-night comedy.

This display of the somber soul of a comedy talk-show host is no surprise to anyone who has followed Stewart over the past decade or so – or who read the lengthy New York magazine profile of him in September. He is as passionate about political issues as any Beltway wonk – and a good sight smarter than many. Like the characters on smarty-pants Hollywood political writer Aaron Sorkin’s “West Wing,” Stewart can toss off a mash-up of policy platforms as glibly as Jimmy Kimmel or Jay Leno might say, “Here’s my next guest.” Does this mean Stewart is approaching the rubicon moment that Sen. Al Franken faced when he crossed over from comedian to candidate?

“Knowing that no matter what was pitched up front about why this rally was happening, when you put a microphone in front of these guys and a crowd full of people, there is a chance that everything could change directions," he says via e-mail. "Take for example the way [comedian Stephen] Colbert changed his testimony at the last second when he appeared before Congress” last month, an ambiguous piece of political performance art that stumped many politicians and even angered a few supporters.

A bigger question that might arise, Mr. Kownacki adds, is “why bother cloaking your agenda in today’s world? If everyone knows who you support and what you stand for, why pretend to be anything less?"